Electric motor assisted super- or turbocharger?

Don Stauffer wrote:

Why not just have a small compressed air pump driven by gears from
crankshaft or camshaft, with a tank to store a few "starts" full of
compressed air? Seems like an easier fix than an electric driven
compressor.



People should really study up on some of the things that have been done
with turbo- and super-chargers for the past 60 years before getting
carried away. For the last 20 years, for example, virtually all EMD
locomotive engines (2-stroke diesels) have used a hybrid
mechanical/turbo supercharger. At low power settings and during
starting, a sprag (overrunning clutch) spins the turbocharger from the
engine's own gear train, just like the old Roots blowers used to be
turned. But when the power is increased, the turbine takes over and
spins the compressor faster than the engine's drive, so the overrunning
sprag releases and the turbo is fully powered by exhaust.

Proven, simple, no silly mechanical-electrical-mechanical conversions to
go through. But the 2-stroke diesel is dead anyway. Conventional
4-stroke turbo-diesels are the present (except for ever-decreasing
production of EMD 710 engines) and the future of diesel power.